Garments possessing buoyancy, cold-resistant and waterproof properties are highly desirable in a multitude of situations. Military personnel equipped with uniforms and jackets having all of these properties would find them advantageous in a number of situations. For example soldier's maneuverability in rough terrain under adverse conditions would be greatly enhanced by clothing which was both cold-resistant to protect the wearer from the elements and simultaneously facilitated crossing a river or fording a stream due to its buoyant and waterproof properties. Mountain climbers and hikers would find such garments similarly advantageous, where crossing a river, dealing with a flood, or resisting the cold are all potential encounters. To achieve their greatest utility, such garments must not only possess these various properties, but they must also be comfortable and not bulky or cumbersome.
Water sports enthusiasts would also find such garments of particular advantage. Indeed, for many activities, garments possessing buoyant, cold-resistant and waterproof properties would be ideal and find great utility.
It is known to provide various garments with foamed materials for thermal insulation. Thus, U.S. Pat. No. 2,976,539 discloses a thermally-insulated garment having an expanded, closed-cell cellular material as a lining, preferably polyvinyl chloride. The garment is thick and cumbersome and does not possess sufficient buoyancy to support a person's weight in water. Similarly, U.S. Pat. No. 3,511,743 discloses a thermal insulation laminate for space and diving suits whose core is an open or closed-cell sponge or foam. A fluid impermeable rubber or plastic skin is necessary. The laminate gives moderate mobility, but is still fairly cumbersome and does not have sufficient buoyancy to serve as a life-saving device.
Polyethylene foams have been suggested as insulation or fillers for life rafts and jackets. U.S. Pat. No. 3,067,147 suggests a low density polyethylene foam for such a purpose which is processed with 1,2-dichlorotetrafluoroethene as a foaming or blowing agent. The polyethylene and blowing agent pressure and explosively extruded into the atmosphere to form an expanded cellular mass. The product is bulky and cumbersome when used in practice. Similarly, U.S. Pat. No. 3,819,543 discloses a molded chlorinated, cross-linked polyethylene foam for use in producing floats and linings for clothing. Various known blowing and cross-linking agents are suggested for use by this reference. The molded products are thick and cumbersome.
Despite these advances, there remains a need for a thin, lightweight material for use as a liner for garments and outdoor equipment which possesses a combination of superior buoyancy, cold-resistant and water-resistant properties, without hampering the mobility of the wearer.